1. Field of the Invention
The present invention relates to a shipping planning system for deciding the shipping quantity of a product and the price of the product so as to increase the profit in consideration of the relationship between the price and the demand and the available amount of the resource on hand and the additional procurement cost.
2. Description of Related Art
In the manufacturing industry, it is a key issue of when, how many and which products to produce and to ship to maximize the profit under the restriction of the limited resources. This issue is generally treated as a product mix issue with profit being the evaluation index. The solution for the issue has been conventionally researched and developed in the field of operations research. For example, the Linear Programming method is a typical approach to solve the problem how much of which product should be produced and shipped to maximize the profit under the restriction of the resources for a predetermined amount of demand of each product. In order to discretely treat the number of the products or resource consumption units in a more practical manner, the problem may be treated as a Combinatorial Optimization Problem to be solved by Mixed Integer Programming or various Heuristic Methods.
In order to evaluate the profit, the price of a product and the cost of producing the product need to be taken into consideration. In many of the conventional researches, the price of the product and the cost are treated as predetermined parameters being a fixed value for each product. However, if the problem is to be treated as a practical matter, the price and the cost need to be treated with attention to the points below.
As is demonstrated in the fields of economy or marketing, the price and the demand are often associated with each other. It may not be practical to consider the price being fixed regardless of the shipping quantity. Therefore, it is appropriate to take the price to be determined according to the shipping quantity instead of a previously given fixed value.
The cost is divided into a fixed cost that fixedly occurs regardless of the shipping quantity and a variable cost that is incurred according to the shipping quantity such as a procurement cost of a material. As the fixed cost is constant no matter what shipping quantity is set for each product, it is not appropriate to take the fixed cost into consideration in decision-making. Therefore, it is preferable to use the marginal profit that is calculated by the sales/variable cost for evaluating the profit by taking only the variable cost which is incurred according to the size of the shipment into consideration in examining when how much of which product is to be produced and shipped. For correct decision making, only the cost that fluctuates according to the result of the decision-making should be taken into consideration. As the cost that has occurred at the moment of the decision-making is the sunk cost from the viewpoint of an actual cost occurrence even if the cost is classified as the variable cost, the cost should not be incorporated in the profit evaluation. In the manufacturing industry, the material procurement cost can be classified as the variable cost according to the number of the product to be produced and the shipping quantity. The procurement cost of the material that has been incurred in the past and is determined to be stored is the cost that occurred regardless of the production and the shipment of the products thereafter; the cost should be subtracted in evaluating the profit when the profit is evaluated. That is to say, the variable cost for a product may change depending on whether the procurement cost of the material to be consumed has already been incurred or to be additionally incurred thereafter.
The above-mentioned practical requirements have been pointed out and have been recognized, but no technique for solving the problem with the requirements for both the price and the cost being actually taken into consideration for providing a solution has been developed yet.
A method for deciding the shipping quantity and the price so as to ensure the product by regarding the price as what changes depending on its relationship with the shipping quantity of a product is disclosed in “Financial Analysis for Profit-driven Pricing, G. E. Smith, T. T. Nagle Sloan Management Review, Spring 1994”. That method is a method for selecting the price so as to ensure the profit according to the predicted fluctuation of the sold number when the current price is changed. With that method, the price is decided based on the Breakeven Sales Volume calculated by the formula below.Breakeven Sales Volume=Current Contribution Margin×current number of sales/Modified Contribution Margin
Here, Current Contribution Margin=current price−current variable cost, and Modified Contribution Margin=Modified price-Modified variable cost. If the predicted sales number ensures the Breakeven Sales Volume, it is determined that the price can be changed higher or lower. In that method, however, how the amount of resources to be consumed changes according to the shipping quantity is not taken into consideration. Thus, there is a problem in that the sunk cost can also be included in the variable cost used in the evaluation.
The invention disclosed in JP-A-2001-154722, for example, is a technique for deciding the shipping quantity, by which the additional procurement cost is the least, by excluding the procurement cost of the material that has been in the inventory from the variable cost as a sunk cost. In JP-A-2001-154722, a production planning system for eliminating a surplus material with the least loss by taking the material that has been in the inventory as the surplus material is provided. That system enables correct decision-making to be performed without incorporating the sunk cost in the cost evaluation by treating only the procurement cost of the material that needs to be additionally procured for producing a product with a surplus material as an additional variable cost. The price setting and the profit evaluation are not supported from the viewpoint of what price the product sells for against the demand (a method for presenting a price required for ensuring a profit based on the cost is shown).
As mentioned above, in the conventional technique, a method for deciding the shipping quantity and the price by a profit evaluation that takes into consideration both the relationship between the price and the demand and the relationship between the shipping quantity and the resource additional procurement cost at the same time has not been provided.
By focusing on a certain product, the price according to the shipping quantity and the additional procurement cost for the required resource change at the same time as the shipping quantity changes. Further, by taking it as a whole, a resource is generally shared by products, and the price and the additional procurement cost need to be obtained according to a combination of the shipping quantity of each product that satisfies the restriction on available capacity of the resource. As such, a matter of deciding the shipping quantity and the price so as to maximize the profit under the restriction of the available capacity of the resource is the combinatorial problem. Therefore, the problem could be solved by treating the problem as a mathematical optimizing problem in theory. As a structural reason that no technique for solving the problem has been provided so far, two points below can be thought of.
<Reason 1>
Changing the price of the product according to the shipping quantity means that a value of the sales that is required to calculate the profit is not always proportional to the shipping quantity, which is an operational variable. Thus, a simple Mathematical Optimization Method such as a linear planning method can not be applied.
<Reason 2>
In order to calculate the amount of resource consumed from the shipping quantity and obtain the additional procurement amount, a procedural algorithm based on a rule such as the Material Requirements Planning (MRP) or the production schedule needs to be used, which is difficult to incorporate simply into a mathematical programming model.
The reason below can also be considered from the viewpoint of good operability in actual application.
<Reason 3>
Even if an optimum solution can be obtained by treating the problem as a mathematical optimization problem, processes to induce such a solution are generally not known, thus, it is not necessarily a method easily accepted by a user.